Glia

Glia, or glial cells, are cells of the
central nervous system which
support the main neuron cells. They act as 'nerve glue'
or neuroglia, insulating the neurons, holding them in place and
controlling the flow of nutrients and other chemicals. They also provide
housekeeping functions, removing dead neurons.

There are several types of glial cells, the most important of which are
astrocytes, oliodendrocytes and microglia.

Brain tumours often arise from glial cells. These are called glioma.

Astrocytes

For fuelling neurons, they receive glucose from capiliaries and break it down
to lactate which is released in the fluid surrounding neurons, which then
transport it to their mitochondria to use for energy. In addition they

Astrocytes are star-shaped with arms that wrap around blood vessels
and neurons. They also surround and isolate synapses, preventing the dispersion
of neurotransmitters.

There are special types of astrocyte that can travel around the central
nervous system using extensible pseudopodia ('false feet') to clean up dead
cells. They push themselves against debris, absorbing and digesting it in a
process called phagocytosis. Where necessary, they will divide to handle
significant work.

Oliodendrocytes

Oliodendrocytes provide primary support to axons and produce the insulating
myelin sheath. Myelin is 80% lipid and 20% protein. The sheath appears as a
series of tube segments about 1mm long.

Oliodendrocytes look at bit like many-armed octopi, with paddle-shaped arms
that wrap around axons in the formation of the myelin sheath.

Microglia

These are the smallest glial cells. Like astrocytes, they act as phagocytesto mop up debris. They also represent the immune system in the
brain and are responsible for inflammation when there is brain damage.

Ependymal cells

Ependymal cells line the cavities in the the
CNS and make up the walls of
the ventricles. They create and secrete
cerebrospinal fluid. They also beat
their cilia to help circulate the CSF.

Ependymal cells are also called ependymocytes.

Radial glia

Radial glia are special cells that help the brain develop. They extend fibers
radially out from the ventricular zone, helping neurons migrate to their final
place.